When a 3D CAD model of a part has been uploaded and subsequently approved by a customer, their confirmed order is moved into a scheduling and build queue. All of the part files are downloaded and the geometry is analyzed for any potential manufacturability issues. If any issues do arise, a dialog between a Proto Labs representative and the customer will take place to resolve the problem before the actual build begins.
As the direct metal laser sintering build prep begins, parts are digitally positioned onto the build platform and the necessary support structures are strategically placed onto the part. Automated supports are initially placed followed by supplemental supports done manually to provide a comprehensive final support system. The build prep features process elements similar to that of both stereolithography and selective laser sintering, requiring a support system (like SL) even though parts are sintered into a bed of powder (like SLS). The rapid melting of each metal layer can create residual stresses in the part during DMLS. Supports that hold parts in place are required to prevent any warping that would occur from these stresses as each layer cools.
Build prep technicians then go through a layer-by-layer review of the build to ensure that all of the features are adequately supported for a successful build. Once the review is complete, the technicians will digitally create the required amount of part copies needed for a particular order before it is ultimately sent to the DMLS machine.
The machine begins sintering each layer — first the support structures to the base plate, then the part itself — with a laser aimed onto a bed of metallic powder. After a cross-section layer of powder is micro-welded, the build platform shifts down and a rubber recoater blade moves across the platform to deposit the next layer of powder into an inert build chamber. The process is repeated layer by layer until the build is complete.
When the build finishes, an initial brushing is manually administered to parts to remove a majority of loose powder. Depending on which metal the parts were built in, they’ll receive the appropriate heat-treat cycle while still fixtured in the support systems to relieve any stresses. Parts are then removed from the platform before the support structures are ultimately removed from the parts with a variety of hand tools (files, dremels, etc.). Surfaces where the support structures were touching are also cleaned up by hand, proceeded by any bead blasting and deburring that is needed to finish the parts. Metals parts built in DMLS are nearly 100 percent dense.
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